Lesson Learned: XP as individual rewards? Really?

Essence: If a player/character does something awesome she/he should be rewarded, no question about it. But should that be in the form of XP?
In my opinion, no. If some players receive XP rewards more often than others it may lead to gaps between the character power level which will eventually frustrate the players with lower XP. I think rewards that do not have a permanent effect are better.

Details: When I GMed 2nd Edition D&D I used to ask around the table which players earned special XP rewards at the end of each session. And it was never a problem since the XP to advance a level varied per class and the impact of difference in XP never was so apparent.
Therefore I used to do the same when we began playing 4th Edition. I tried to keep the XP at a minimum but then I faced the problem with players who could not attend.
I went along with the recommendation that players would gain the XP for the sessions they missed but only after they had attend a number of sessions equals to the numbers they had missed. That and the fact that players cannot get XP rewards when absent would have eventually lead to the situation that some players would have advanced a level while others still had to wait for several sessions. Which could be quit frustrating.
Thus did I raise all players to the same XP level and everyone gets the same XP for each session since then. It does not matter if they are missing or attempting. It is bad enough that someone did not make it, but he should not be punished.
Since I like giving rewards as motivation even during the game, I was looking for something that has only a short-term impact on the game in order to prevent gaps between character power levels.
The best thing I have found were rerolls. Even if the effect is limited the usage of a reroll can still be very satisfying for a player. Think of a daily power attack roll which did miss, which can also be very frustrating. Especially if it keeps on happening. And the other players wont feel left behind but will be rooting for the player that uses a reroll.
Currently I cannot see a reason why I should start giving out XP as individual rewards, again. I think even for Con games are rerolls better since the player can cash-in his reward while playing and he can keep up doing more awesome stuff.

Advice: If you introduce short term boosts to characters as a alternative to XP rewards you should consider restricting the usage of the boosts. If a player collects rewards and uses them all during one encounter that challenge might be fun for that player but all others probably wont enjoy it.
Therefore did I restrict the usage of rerolls to one per encounter and a player looses all but one after a extended rest.